The present invention relates to an active matrix liquid crystal display device and particularly relates to a reflective type liquid crystal display device.
In recent years, as such information and communication equipment as portable telephone, PHS (Personal Handy Phone System), PDA (Personal Digital Assistant) and the like springs into wide use, a required infrastructure has been in completion, thereby allowing anyone to access and send out information easily regardless of time and place.
Since such information and communication equipment is used in mobile applications, features such as being thin in size, light in weight and low in power consumption are required of a display system. Nowadays, the liquid crystal display device occupies a central position among such display systems. Among the variety of liquid crystal display devices, a reflective type liquid crystal display device requiring no back light is becoming a main-stream. A typical prior art active matrix reflective type liquid crystal display device is disclosed in Japanese Patent Application Unexamined Publication No. H08-160463.
A description is made on a typical prior art active matrix reflective type liquid crystal display device as follows:
An active matrix reflective type liquid crystal display device has a transparent substrate, many pixel electrodes disposed on the foregoing transparent substrate and non-linear elements to drive respective pixel electrodes.
As the non-linear element is used a thin film diode, a thin film transistor (referred to as TFT hereafter) or the like. These pixel electrodes and non-linear elements are arranged in a two-dimensional matrix pattern.
In the following description, a typical prior art active matrix reflective type liquid crystal display device uses a TFT as the non-linear element.
FIG. 6 shows an opening and a TFT element of a prior art active matrix reflective type liquid crystal display device, and FIG. 6(b) shows a cross-sectional view of the above opening and TFT element and FIG. 6(a) shows a plan view of the opening of FIG. 6(b). In FIG. 6(a), a depiction of a reflective pixel electrode 401 is omitted for easy recognition of the size of the opening.
A gate insulating film 408 is disposed on a glass substrate 410.
A protective film 403 is disposed on the gate insulating film 408. An interlayer insulating film 402 is disposed on the protective film 403. The reflective pixel electrode 401 is disposed on the interlayer insulating film 402. A TFT element 411 has a drain electrode 405, a source electrode 406, a semiconductor layer 407 and a gate electrode 409.
By way of an opening 404 acting as a contact hole, the reflective pixel electrode 401 and the drain electrode 405 become conductive with each other.
In the structure as described above, the distance between the gate electrode 409 acting as a scanning line electrode and the reflective pixel electrode 401 can be shortened and further the distance between the source electrode 406 acting as a signal line electrode and the reflective pixel electrode 401 can be shortened. At the same time, a short circuit between the reflective pixel electrode 401 and the gate electrode 409 and between the reflective pixel electrode 401 and the source electrode 406 can be prevented from occurring by the interlayer insulating film 402, thereby allowing the opening ratio to be increased by a large amount when compared with the case where no interlayer insulating film is used.
However, the prior art active matrix reflective type liquid crystal display device as described above has some problems as in the following:
For instance, with the prior art liquid crystal display device, the size of the opening 404 at the protective film 403 measures 6 xcexcm in the longitudinal length xe2x80x9cXaxe2x80x9d and 6 xcexcm in the lateral length xe2x80x9cYaxe2x80x9d. The size of the opening 404 at the interlayer insulating film 402 measures 15 xcexcm in the longitudinal length xe2x80x9cXbxe2x80x9d and 15 xcexcm in the lateral length xe2x80x9cYbxe2x80x9d. In this case, the dimension of the opening 404 at the protective film 403 and the dimension of the opening 404 at the interlayer insulating film 402 are different from each other.
As a result, a step-wise difference in level [xe2x80x9cAxe2x80x9d in FIG. 6(b)] is formed on the reflective pixel electrode 401 at the boundary of the protective film 403 and the interlayer insulating film 402. Because of this step-wise difference in level, a break in the reflective pixel electrode 401 is likely to occur. When the break occurs in the reflective pixel electrode 401, the electrical continuity between the reflective pixel electrode 401 and the TFT element 411 can not be secured, thereby causing the problem of dot defects to the liquid crystal display device.
In addition, with a liquid crystal display device using pixel electrodes that are formed mainly of aluminum, such defects as poor contact, disconnection and the like are caused by the differences in film thickness of the reflective pixel electrodes, having resulted in such problems as a display failure, a reduction in reflectivity and the like
The present invention provides a liquid crystal display device, which enables the prevention of a break in pixel electrodes from occurring and the realization of excellent display characteristics, and provides a video display apparatus and an information processing apparatus using the foregoing liquid crystal display device.
A display device which employs a liquid crystal material of the present invention comprises:
a transparent substrate;
nonlinear elements, each of which has a plurality of electrodes, disposed on the transparent substrate;
a protective film disposed on each respective nonlinear element of above;
an interlayer insulating film disposed on the protective film; and
a pixel electrode disposed on the interlayer insulating film, in which an opening with the cross-section thereof configured in a V-letter like slanting shape is formed in the protective film and interlayer insulating film, respectively, the openings are exposed to the surface of the nonlinear element, one of the openings is provided with a first end part formed on the protective film and the other is provided with a second end part formed on the interlayer insulating film, the first end part is located outside of the second end part, the pixel electrode is also disposed on the interlayer insulating film of the opening and an electrode out of the plurality of electrodes of the nonlinear element is in contact with the pixel electrode in the opening.
A manufacturing method of display device employed liquid crystal material of the present invention comprising the steps of:
(a) disposing a nonlinear element having a plurality of electrodes an a substrate
(b) disposing a protective film with covering said nonlinear element, in which said protective film has a lower opening, and a first electrode of said plurality of electrodes exposes at said lower opening,
(c) disposing a interlayer insulating film with covering said protective film, in which said interlayer insulating film has an upper opening formed at a place according to said lower opening, and said first electrode exposes at said upper opening, and
(d) disposing a pixel electrode with covering said interlayer insulating film and said first electrode,
wherein said lower opening and said upper opening formed a opening,
said opening has a V-letter like slanting shape,
said opening has a first end part formed on said protective film and a second end part formed on said interlayer insulating film, and
said opening is formed so that said first end part is located outside of said second end part.
According to the above structure, dot defects are prevented from occurring and missing of pixels is prevented, thereby realizing a display device with excellent display characteristics such as a bright display screen and the like. Furthermore, the yield rate of conforming display devices is remarkably improved.
A video display apparatus of the present invention employs the display device as described above. The video display apparatus thus configured shows excellent display characteristics in the same way as described above.
An information processing apparatus of the present invention employs the display device as described above. The information processing apparatus thus configured shows excellent display characteristics in the same way as described above.